Ultrasonic transducer and method for manufacturing the same

An ultrasonic transducer, comprising:

• a rigid substrate comprising a plurality of opening parts penetrating the rigid substrate between a bottom surface and a top surface thereof;
• a flexible resin film that is fixed to the top surface of the substrate so as to cover the plurality of opening parts;
• a plurality of piezoelectric elements that are fixed to a top surface of the resin film so as to overlap with the plurality of opening parts, respectively, in a plan view;
• a lower sealing plate that includes a central opening with a size surrounding an opening part forming region in which the plurality of opening parts of the rigid substrate are formed, and that is fixed to the top surface of the flexible resin film so that the central opening surrounds the opening part forming region in the plan view;
• and
• a wiring assembly fixed to a top surface of the lower sealing plate,
• wherein the wiring assembly includes an insulating base layer, first and second conductor layers that are arranged on the base layer and are electrically connected to a pair of first and second application electrodes, respectively, of the piezoelectric element, and an insulative cover layer,
• wherein each of the first and second conductor layers has an external-side terminal region and a piezoelectric element-side terminal region, and
• wherein the cover layer encloses the first and second conductor layers in a state where at least the external-side terminal region and the piezoelectric element-side terminal region are accessible.

An ultrasonic transducer comprising:

• a rigid substrate that is provided with a plurality of opening parts penetrating the rigid substrate between a bottom surface and a top surface thereof,
• a flexible resin film that is fixed to the top surface of the substrate so as to cover the plurality of opening parts;
• a plurality of piezoelectric elements that are fixed to a top surface of the resin film so as to overlap with the plurality of opening parts, respectively, in a plan view;
• a lower sealing plate that includes a central opening with a size surrounding an opening part forming region in which the plurality of opening parts of the rigid substrate are formed, and that is fixed to the top surface of the flexible resin film so that the central opening surrounds the opening part forming region in the plan view;
• and
• a wiring assembly fixed to a top surface of the lower sealing plate,
• wherein the piezoelectric element includes a piezoelectric element main body, an inner electrode that partitions the piezoelectric element main body into a first piezoelectric portion on an upper side and a second piezoelectric portion on a lower side in a thickness direction, a top surface electrode fixed to a part of a top surface of the first piezoelectric portion, a bottom surface electrode that is fixed to a bottom surface of the second piezoelectric portion and forms an outer electrode along with the top surface electrode, an inner electrode connection member of which one end part is electrically connected to the inner electrode and the other end part forms an inner electrode terminal accessible at the top surface of the first piezoelectric portion while being insulated from the top surface electrode, and a bottom surface electrode connection member of which one end part is electrically connected to the bottom surface electrode and the other end part forms a bottom surface electrode terminal accessible at the top surface of the first piezoelectric portion while being insulated from the top surface electrode and the inner electrode,
• wherein the wiring assembly includes an insulating base layer, an outer electrode conductor layer and an inner electrode conductor layer arranged on the base layer, each of which has an external-side terminal region and a piezoelectric element-side terminal region, and a cover layer that encloses the outer electrode conductor layer and the inner electrode conductor layer in a state where at least the external-side terminal region and the piezoelectric element-side terminal region are accessible,
• wherein the base layer includes a plurality of piezoelectric-element overlapping portions that partially overlap with the plurality of piezoelectric elements, respectively, in a plan view, and a distal end portion that integrally supports the plurality of piezoelectric-element overlapping portions,
• wherein the piezoelectric-element overlapping portion includes an outer electrode tab region having an outer electrode connection opening and an inner electrode tab region having an inner electrode connection opening,
• wherein the piezoelectric element-side terminal region of the outer electrode conductor layer has a bridge shape that extends across the outer electrode connection opening and is supported at a distal end side by the outer electrode tab region,
• wherein the piezoelectric element-side terminal region of the inner electrode conductor layer has a bridge shape that extends across the inner electrode connection opening and is supported at a distal end side by the inner electrode tab region,
• wherein the wiring assembly is fixed to a top surface of the lower sealing plate in a state where the outer electrode connection opening overlaps, in the plan view, with a part of the top surface electrode and the bottom surface electrode terminal of the corresponding piezoelectric element and the inner electrode connection opening overlaps, in the plan view, with the inner electrode terminal of the corresponding the piezoelectric element,
• wherein a portion of the piezoelectric element-side terminal region of the outer electrode conductor layer that extends across the outer electrode connection opening is electrically connected to the part of the top surface electrode and the bottom surface electrode terminal of the corresponding piezoelectric element, and
• wherein a portion of the piezoelectric element-side terminal region of the inner electrode conductor layer that extends across the inner electrode connection opening is electrically connected to the inner electrode terminal of the corresponding piezoelectric element.

A manufacturing method of an ultrasonic transducer comprising:

• a rigid substrate forming step of forming a rigid substrate including a plurality of opening parts that penetrate the rigid substrate between a bottom surface and a top surface thereof by etching a rigid plate material;
• a flexible resin film fixing step of fixing a flexible resin film to the top surface of the rigid substrate so as to cover the plurality of opening parts by an adhesive or by thermocompression bonding;
• a piezoelectric body assembly forming step of preparing a plurality of two-layer laminated type piezoelectric elements each configured so that a top surface electrode, a bottom surface electrode terminal electrically connected to a bottom surface electrode that forms an outer electrode along with the top surface electrode and an inner electrode terminal electrically connected to an inner electrode are accessible from the upper side, and then fixing the plurality of piezoelectric elements to the top surface of the flexible resin film by an insulating adhesive so that the plurality of the piezoelectric elements overlap with the plurality of opening parts, respectively, in a plan view to form a piezoelectric body assembly;
• a lower sealing plate arranging step of preparing a lower sealing plate that includes a central opening having a size surrounding an opening part forming region in which the plurality of opening parts of the rigid substrate are formed, and then fixing the lower sealing plate to the top surface of the flexible resin film by an adhesive so that the central opening surrounds the opening part forming region in the plan view,
• a wiring assembly preparation step of preparing a wiring assembly that includes an insulating base layer, an outer electrode conductor layer and an inner electrode conductor layer arranged on the base layer, each of which has an external-side terminal region and a piezoelectric element-side terminal region, and a cover layer that encloses the outer electrode conductor layer and the inner electrode conductor layer in a state where at least the external-side terminal region and the piezoelectric element-side terminal region are accessible, wherein the base layer includes a plurality of piezoelectric-element overlapping portions that partially overlap with the plurality of piezoelectric elements, respectively, in the plan view, and a distal end portion that integrally supports the plurality of piezoelectric-element overlapping portions, wherein the piezoelectric-element overlapping portion includes an outer electrode tab region having an outer electrode connection opening and an inner electrode tab region having an inner electrode connection opening, wherein the piezoelectric element-side terminal region of the outer electrode conductor layer has a bridge shape that extends across the outer electrode connection opening and is supported at a distal end side by the outer electrode tab region, wherein the piezoelectric element-side terminal region of the inner electrode conductor layer has a bridge shape that extends across the inner electrode connection opening and is supported at a distal end side by the inner electrode tab region;
• a wiring assembly fixing step of fixing the wiring assembly to the top surface of the lower sealing plate by an insulating adhesive in a state where the outer electrode connection opening overlaps in a plan view with a part of the top surface electrode and the bottom surface electrode terminal of the corresponding piezoelectric element, and the inner electrode connection opening overlaps in a plan view with the inner electrode terminal of the corresponding piezoelectric element;
• an electric connection step of electrically connecting a bridge portion of the piezoelectric element-side terminal region of the outer electrode conductor layer to both a part of the top surface electrode and the bottom surface electrode terminal of the corresponding piezoelectric element, and electrically connecting a bridge portion of the piezoelectric element-side terminal region of the inner electrode conductor layer to the inner electrode terminal of the corresponding piezoelectric element,
• wherein the wiring assembly preparation step is performed independently from the rigid substrate forming step, the flexible resin film fixing step, the piezoelectric body assembly forming step and the lower sealing plate arranging step, at least before the wiring assembly fixing step.